What NHIS Variables are missing from IHIS?


I am new to NHIS data and am trying to understand what are the main NHIS variables missing in IHIS. In the FAQ IHIS notes “Variables from the original NHIS public use files (that are not yet in the IHIS system). . .”

IHIS seems pretty comprehensive, so what is missing? Is there a large number of variables missing? Are the variables that are missing related to certain topics? years?

I want to use data from 1998-2012. Thanks!